217630647081 has 27 divisors (see below), whose sum is σ = 328665860887. Its totient is φ = 138758436960.

The previous prime is 217630647061. The next prime is 217630647119. The reversal of 217630647081 is 180746036712.

The square root of 217630647081 is 466509.

It is a perfect power (a square), and thus also a powerful number.

217630647081 is a `hidden beast` number, since 2 + 1 + 7 + 630 + 6 + 4 + 7 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 173631389481 + 43999257600 = 416691^2 + 209760^2 .

It is not a de Polignac number, because 217630647081 - 2¹³ = 217630638889 is a prime.

It is a super-2 number, since 2×217630647081² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217630647061) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 32185741 + ... + 32192501.

Almost surely, 2^217630647081 is an apocalyptic number.

217630647081 is the 466509-th square number.

217630647081 is the 233255-th centered octagonal number.

It is an amenable number.

217630647081 is a deficient number, since it is larger than the sum of its proper divisors (111035213806).

217630647081 is an frugal number, since it uses more digits than its factorization.

217630647081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13574 (or 6787 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 45.

The spelling of 217630647081 in words is "two hundred seventeen billion, six hundred thirty million, six hundred forty-seven thousand, eighty-one".